The present invention concerns a chair having a reclineable back and a vertically adjustable lumbar device for the back.
Manufacturers are becoming increasingly aware that adequate lumbar support is very important to prevent lower back discomfort and distress in humans who are seated for long periods. A problem is that the spinal shape and body shape of humans vary tremendously, such that it is not possible to satisfy all humans with the same shape of back support. Further, the desired level of freeness or force of support in the lumbar area is different for each person and may vary as a seated user performs different tasks and/or reclines in the chair and/or becomes fatigued. In fact, a static lumbar support is undesirable. Instead, it is desirable to provide different lumbar shapes and levels of support over a work day. Accordingly, an adjustable lumbar system is desired that is constructed to vary the shape and force of lumbar support. At the same time, the adjustable lumbar system must be simple and easy to operate, easily reached while seated, mechanically non-complex and low cost, and aesthetically/visually pleasing. Preferably, adjustment of the shape and/or force in the lumbar area should not result in wrinkles in the fabric of the chair, nor unacceptable loose/saggy patches in the fabric. Further, lumbar adjustable devices are wanted that are intuitive to operate and also that are field-installable by the users themselves.
Recently, a new chair has been developed by Steelcase that includes a very flexible back construction adapted to flex significantly in the lumbar region of a seated user""s back, and further that is biased in the lumbar region to provide good support to a seated user. The result is a very comfortable back that posturally supports a user as the user moves around in the chair. The back construction not only provides excellent postural support, but it also minimizes shirt pull as a seated user moves between upright and reclined positions. A potential problem is that this back construction flexes to such an extent that it is difficult to eliminate wrinkles and looseness in upholstery covering the back construction in all flexed positions of the back construction, particularly as the back construction is flexed from a deep concave condition where the lumbar region protrudes forwardly, and then is flexed toward a more planar condition where the lumbar region is more aligned with the thoracic and pelvic regions of the back construction. During this flexure, there is a significant change in vertical length along a front surface of the back construction as the back construction is flexed, such that the covering tends to wrinkle and become loose as the lumbar region is flexed toward the more planar condition. The problem is further compounded by the need to have a chair assembly process that minimizes parts, cost, and labor. Still further, the particular new chair design illustrated herein has a novel and attractive rear appearance of the back construction and lumbar adjustment device that, in many circumstances, is desirable not to hide or cover. Thus, an upholstery arrangement is desired that attaches to and is limited primarily to a front surface of the back construction, yet that is secure, durable, and closely retained to the back support structure to prevent looseness and bunching of the covering.
Accordingly, a chair construction solving the aforementioned problems is desired.
In one aspect of the present invention, a seating unit includes a flexible back including a non-planar lumbar region, and a tensioned cover stretched over the non-planar lumbar region. A lumbar device is fit between the front surface and the covering, with a tension of the covering biasing the lumbar device against the lumbar region and resulting in a frictional force retaining the lumbar device in a selected vertical position.
In another aspect of the present invention, a back for a seating unit includes a flexible back shell including a non-planar flexible lumbar region, and a cover covering at least a portion of the non-planar flexible lumbar region. A lumbar device fits between the front surface and the covering, the lumbar device being vertically adjustable and being made of a material chosen to generate friction with the lumbar region and with the cover to retain the lumbar device in a selected vertical position.
In another aspect of the present invention, a method includes steps of providing a flexible back including a non-planar lumbar region of a seating unit, providing a cover shaped to cover at least a portion of the non-planar lumbar region, and tensioning the cover over the lumbar region. The method further includes providing a lumbar device, and fitting the lumbar device between the front surface and the covering, with a tension of the covering biasing the lumbar device against the lumbar region and resulting in a frictional force retaining the lumbar device in a selected vertical position.
In yet another aspect of the present invention, a method includes steps of providing a seating unit having a back support with a front surface, covering at least a portion of the front surface with a sheet back covering, and positioning a lumbar device between the front surface of the back support and the portion of the back covering. The method further includes vertically adjusting the lumbar device to a selected height and holding the lumbar device in place with friction between the back support and the back covering.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.